This invention relates to an insulated elongate conduit member and an assembly therefor, and a method of joining insulated elongate conduit members. The invention is particularly but not exclusively suitable for joining insulated pipes. Although the invention relates in general to the joining of insulated elongate conduit members, the description below will relate primarily, for convenience and not by way of limitation, to the joining of thermally insulated pipes, suitable for use in a district heating system, or a district cooling system.
In the installation of insulated pipes comprising a fluid conveying pipe, and a covering layer of thermal insulation, it is necessary to make joints between adjacent sections of pipe. After joining the pipes, it is necessary to ensure that there is adequate thermal insulation around the joint in order to minimise heat losses from the system.
Hitherto, the end portion of an insulated pipe has been bared of insulation to facilitate joining to the bared end portion of another insulated pipe by for example welding, brazing or soldering. It is then necessary to reinsulate the bared pipes in the region of the joint. One method that has been used to reinsulate the bare portion of the pipes is to position a tubular case around said bare portion, introduce insulating foam to fill the cavity surrounding the bare portion through an opening in the case, and then provide an environmental sealing layer, of for example heat-recoverable polymeric material, around the case. One major disadvantage, however, is that a different size case must be provided for each different sized insulated pipe; this means that a large inventory must be carried. Another problem is that the introduction of foam into the cavity within the case around the pipe joint does not always lead to a well insulated joint, and the foaming process itself is potentially hazardous to the operator. Yet another problem is that the method described above is time-consuming.
A further problem lies in the vulnerability of the bare ends of insulated pipes to damage before installation, which can result in a pipe being substantially weakened, or deformed to an extent that it cannot be joined to the end of another pipe.